Actuators are commonly used to control a variety of devices. The actuator provides the force needed to move and position a valve. The pressure differential between the inlet and outlet, which causes flow through the valve, can produce a force on the valve that opposes the force of the actuator. This may require the use of a larger and more expensive actuator. The force, caused by the pressure differential, can be reduced by using a diaphragm with a flexible convolute. The outer circumference of the diaphragm is secured and sealed within the actuator/valve. The inner portion of the diaphragm is secured and sealed to a moving component associated with the valve such as the valve stem or armature. The flexible convolute of the diaphragm will allow the valve to move through its stroke.
A sealed cavity above the diaphragm will receive the same pressure that is applied to the valve at the inlet. A passageway may be formed in a component such as a valve insert. The effective area of the diaphragm and the area valve are made approximately equal. The forces, caused by the pressure, acting on the valve and diaphragm will cancel each other and reduce or eliminate the need for a higher force actuator. A disadvantage of the diaphragm is potential damage to the convolute caused by high pressure and the stress of movement.
If the pressure is high, the diaphragm may balloon and be damaged. If this occurs, the result may be a failure that would cause the valve to open or have leakage between the valve inlet and outlet. Therefore, it would be desirable to have to have a method of balancing the pressure without using a diaphragm.